1. Field of the Invention
The present invention relates to a land grid array socket for electrically connecting a CPU to a printed circuit board.
2. The Prior Art
Land grid array (LGA) sockets are commonly used with IC packages and do not require soldering procedures during engagement between the LGA socket and a related mother board. Normally, an LGA assembly includes an IC package having a plurality of flat contact pads formed on a bottom surface thereof, a socket having an insulative housing and defining a plurality of passageways therethrough, an d a plurality of conductive contacts received in the passageways of the socket. Fastening means consisting of a top plate positioned on a top surface of the IC package, a bottom plate positioned on a bottom surface of the PCB, and a plurality of sets of aligned holes defined through the PCB, the top plate and the bottom plate is used to configure the assembly. Each set of aligned holes receives a screw therein which engages with a washer and a nut thereby sandwiching the LGA assembly between the top and bottom plates of the fastening means.
U.S. Pat. No. 5,653,598 discloses an electrical contact for use in a connector 30 between mutually opposed electrical interfaces 40, 99 such as contact pads respectively formed on an IC package 2 and a printed circuit board 9, as shown in FIG. 12. The conventional contact comprises a generally planar contact body 10 having first and second major faces 110, 120. The body 10 includes a pair of spaced apart spring arms 140, 150 connected by a resilient bight portion 160. The spring arms 140, 150 each have a free end with an outwardly facing edge forming a contact nose 17, 18 for engaging with the corresponding interface 40, 99. Shorting sections 19, 20 generally extend toward each other from the free ends and are offset such that, upon deflection of the spring arms 140, 150 toward each other, the shorting sections 19, 20 overlap and the first major face 110 engages the second major face 120. Thus, a shortened electrical path is formed between the contact noses 17, 18 when the package 2 is urged against the connector 30.
The electrical interface 40 of the IC package 2 may not be able to properly abut against the contact nose 17 of the contact body 10 due to misalignment when the IC package 2 and the printed circuit board 6 are forced to sandwich the connector 30 by a clip or screws. Therefore, it is requisite to provide a positioning structure on the connector to effectively fix the IC package in the connector before an external clamping force is applied on the IC package.
Moreover, the shorting sections 19, 20 may not properly contact each other due to unwanted lateral deflection thereof when the bight of the contact is deformed. Although the inner wall of the passageway receiving the contact may be used to limit the lateral deflection of the shorting sections 19, 20, unwanted scraping of the shorting sections 19, 20 against the inner wall of the passageway may occur thereby adversely affecting the proper overlap of the two shorting sections 19, 20. Proper overlap and engagement of the two shorting sections 19, 20 is difficult to achieve with this structure. Moreover, an additional contact resistance exists between the shorting sections 19, 20 thereby adversely affecting the signal transmission. Additionally, the spring arms 140, 150 occupy too much space especially in the length thereof which causes impossible for fine pitch requirement. It is requisite to provide a new LGA contact which can provide a relatively short transmission path without introducing an additional contact resistance.